Low-water alarm.



H. B. THURSTON.

LOW WATER ALARM.

APPLICATION FILED AUG-30.1916.

I1. lfl mu Patented June 26, 191?.

WITNESSES 575 A TTOH/VEYS HERMAN B. THUBSTON, 0F GRAFTON, PENNSYLVANIA.

LOW-WATER. ALARM.

Specification of Letters Patent;

Patented June ac, rem.

Application filed August 30, 1916. Serial No. 117,779.

To all whom it may concern Be it known that I, HERMAN TON, a citizen ofthe United States, and a resident of Grafton, in the county of Allegheny and State of Pennsylvania, have invented new and useful Improvements in Low-Water Alarms, of which the following is a specification. I

My present invention relates generally to low water alarms, and more particularly to that type of device which is secured in the crown sheet of a boiler, and includes a fusible element normally controlling the egress of steam, the device so constituted being connected to a posterior alarm signal so that upon fusing of the fusible member, the escape of steam will sound the alarm.

The object of my present improvements, among others, is to provide a device wherein the fusible member will be well protected'in all respects against premature action, and wherein it may be readily removed through the fire box for'cleaning purposes, and auto matically freed from incrusting scale by its removal.

To this end generally speaking, I provide a case, which in the first'instance is threaded through the crown sheet of a boiler, and which after disposition in such manner, and connection with its alarm signal, need not thereafter be removed for any purpose except possibly its own repair, the fusible element being carried by, and wholly remov-- able from the case with a plug threaded into the case from its lower end, and consequently the fire box side of the crown sheet, so as to be readily removable at all times for cleaning and repair, through the fire box itself.

- In the accompanying drawings in which my invention is illustrated,

Figure 1 is a side elevation, partly broken away and in section, of a boiler equipped with my improved low water alarm.

Fig. 2.is a vertical sectional view taken substantially on the line 22 of Fig. 1.

Fig. 3 is a top plan view, partly broken away and in section, of the case.

Fig. 4 is a side elevation thereof.

Fig. 5 is a top plan view of the plug, and

Fig. 6 is a side elevation thereof.

Referring now to these figures in which the boiler is generally indicated at 10 and the crown sheet at 11, the chambered case 12 is in accordance with my invention, externally threaded in order. that it may be screwed into and through a threaded open- B. THURS- I ing of the crown sheet 11, in the manner best shown in Fig. 2, the case having at its upper end a threaded nipple 13 whereby it may be connected to a pipe 14 leading exteriorly through the top wall 15 of the boiler 10 and to a posterior alarm signal, as indicated at 16 in Fig. 1, for instance, an alarm whistle.

The lower end of the case 12 opens into the fire box 17 and its chamber 18 communicateswith side openings 19 above the crown sheet, and with a bore 20 leading through the nipple 13, the internal portion of the said case between its chamber 18 and its lower open end, being threaded as at 21 for the reception of the externally threaded plug 22, the latter of which screws upwardly through the lower open end of the case.

The plug 22 is recessed at its inner end for the reception of a fusible filling 23, this recess including a bore leading axially within the inner end of the plug and communicating with side openings, and the filling 23 extending into both said bore and said side openings, and being at the latter, extended and threaded to forma part of the threaded external surface of the plug, as seen particularly by reference to Figs. 2 and 6.

The fusible-filling 23 is also extended beyond the inner end of the plug 22, as shown particularly 'at2 1, and is adapted therefore to extend within an annular counter-bore 25 internally of the case 12 and around the lower end of the bore 20, before mentioned, so that when the plug is forced with Suficient pressure into the case, the fusible .filling 23 being of comparatively soft material, will be pressed to completely fill the counterbore 25 and form an eflective seal to prevent leakage and egress of pressure from the boiler space to the alarm whistle 16.

The internally threaded portion 21 of the 1 case 12 is reduced so as to form an internal annular shoulder 26 adjacent the lower end of the said case, against which the annular flange 27 at the lower end of the plug 22 ice I abuts to form an effective seal against lea-k alarm, the plug 22 may be readily screwed out of the case 12, and in so doing will break and automatically remove therefrom,-

7 against the intense heat of the firebox 17 and will be cooled. by the water of the boiler space when the latter. is near its normal level. I

In operation, when the water falls to a dangerously low extent within the boiler space, the material increase in heat will fuse the-filling 23 andthus open up a direct passage through the bore 20 for the passage of the steam to the alarm whistlelfi.

I claim:

In a device of the" character described, a casing having a chamber and lateral openings through its wall communicating with said chamber, said casing also having an axial opening and an axial-bore at opposite sides of its chamber and an outer valve seat at the outer end of its said bore, and provided with a counter bore around the inner end of the axial opening forming an inner valve seat at one side of the chamber, and a plug having a solid body externally threaded for engagement in the said hereof the easing and provided with an enlarged head at one end. for engagement against the said outer'valve seat, said plug having its inner end recessed within the chamber, and a fusible filling anchored within the recess ofthe plug and extending beyond the same for engagement against the said inner valve seat' I HERMAN B. THURSTON.

Witnesses: I u

I'IERBERT LEWIs, FRED B. FISHER. 

